We present evidence for an expanding superbubble in M 82 ( diameter : \approx 130 pc , expansion velocity : \approx 45 km s ^ { -1 } , mass : \approx 8 \cdot 10 ^ { 6 } M _ { \odot } ) .
It is seen in the ^ { 12 } { CO } \ ( J = 1 \to 0 ) , ^ { 12 } { CO } ( J = 2 \to 1 ) , ^ { 13 } { CO } ( J = 1 \to 0 ) and { C } ^ { 18 } { O } \ - ( J = 1 \to 0 ) lines .
The superbubble is centred around the most powerful supernova remnant , 41.9+58 .
The CO observations show that the molecular superbubble already broke out of the disk .
This scenario is supported by ROSAT HRI observations which suggest that hot coronal gas originating from inside the shell is the main contributor to the diffuse X–ray outflow in M 82 .
We briefly discuss observations of the same region at other wavelengths ( radio continuum , optical , H I , X–rays , ionized gas ) .
From our spectral line observations , we derive a kinematic age of about 10 ^ { 6 } years for the superbubble .
Using simple theoretical models , the total energy needed for the creation of this superbubble is of order 2 \times 10 ^ { 54 } ergs .
The required energy input rate ( 0.001 SN yr ^ { -1 } ) is reasonable given the high supernova ( SN ) rate of \approx 0.1 SN yr ^ { -1 } in the central part of M 82 .
As much as 10 % of the energy needed to create the superbubble is still present in form of the kinetic energy of the expanding molecular shell .
Of order 10 % is conserved in the hot X–ray emitting gas emerging from the superbubble into the halo of M 82 .
This newly detected expanding molecular superbubble is believed to be powered by the same objects that also lie at the origin of the prominent X–ray outflow in M 82 .
It can therefore be used as an alternative tool to investigate the physical properties of these sources .